Systematic evolution of ligands by exponential enrichment (SELEX) is a combinatorial technique in molecular biology for producing oligonucleotides of either single-stranded DNA or RNA that specifically bind to a target ligand or ligands. Such conventional procedures can be based on isolating binders from large libraries of random synthetic oligonucleotides. This method can produce strong binding aptamers to a desired ligand, but some ligands (e.g., glucose) have no known aptamers. This may occur because such molecule has no chemically functional groups that will bind the nucleotides. For example, there are no suitable aptamers (e.g., small, practical to synthesize, with high affinity) against sugars such as glucose, fatty acids or related long-chain lipids, or amino acids such as glycine or leucine.